A new lab tech has been hired for the quality control of concrete. The new perso

Question

A new lab tech has been hired for the quality control of concrete. The new person does not have any experience. He has been instructed to produce concrete, put it in 4 by 8 in. cylinder molds, cure it in the moist cure room and test it for compression at 28 days. However, due to his lack of experience, and being shy and afraid to ask, the concrete cylinders were never demolded and the compressive strength was tested on the concrete still in the molds. Do you think the assessed concrete strength would be affected? If yes, explain why. If no, explain why not.

Explanation / Answer

The assessed concrete strength will be on the higher side as the test is conducted along with the mould.

Since the mould will act as an encasement for the concrete and act as a confinement for the lateral deformation of concrete.

The failure of the concrete specimen when tested under compression is due to the lateral tensile stresses induced by the lateral stress (poisson's effect). But in the present case the mould will restrict the lateral expansion of concrete and thus giving the strength on higher side.

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